This invention relates to a medical device that provides enhanced image and response to an ultrasound signal and more particularly to a surgical needle having geometric features that provides an enhanced image and response.
Ultrasonic imaging has long been used in medical practice to provide images not only of body organs and parts but also of the medical instruments and in particular needles that are used in connection with various medical procedures.
For example, ultrasonic imaging is used to guide a medical needle into a body part to effect a biopsy, to access fluid collection for sampling or drainage, to obtain vascular access and to access the urinary and biliary tracts. Ultrasonic imaging is also used to place a needle at a tumor or other body structure for subsequent surgical removal.
A major limitation on the ultrasonic guided intervention or procedures are the inability to image the medical instrument or needle adequately in many circumstances. The visibility of the needle is strongly dependent on the particular geometrical relationship between the transducer that provides the ultrasonic beam and the reflective surface of the instrument. The amount of ultrasonic energy reflected from the instrument toward the transducer (an ultrasonic echo sensor) determines the quality of the image of the instrument on the monitor. If the needle is in the plane of the interrogating ultrasonic beam and horizontal to the face of the sensing transducer, or perpendicular to the direction of the incident beam, the reflected energy is optimized and a usable visible image is obtained. However, as the needle becomes less perpendicular to the direction of the incident beam, lesser amounts of ultrasonic energy are reflected to the sensor and the instrument is imaged poorly or not at all.
The optimal geometric relationship is difficult to maintain in all but fairly limited applications of ultrasonic guided interventions. It becomes nearly impossible to maintain the optimum geometry in many instances because of intervening organs or structures. This results in poor visualization of the instrument, procedure time is lengthened and complexities are created which would not be present if the needle were easily seen.
Multiple passes with a needle may have to be made before it can be visualized causing tissue damage within adjacent organs or structures and creating the potential of bleeding and other complications. There are times when the physician is able to visualize the target lesion quite well but not the needle or other instrument. Moving the sensing transducer can result in the needle being imaged but the image of the target lesion is lost. A series of trial and error maneuvers are employed. Breathing motion of the patient further complicates the process.
This problem has been addressed by a large number of proposed designs, including those shown in U.S. Pat. No. 4,869,259, No. 4,977,897, No. 5,048,530, No. 5,081,997, No. 5,213,569, No. 5,221,269, No. 5,383,466, No. 5,490,521, No. 5,611,345, No. 5,766,135 and No. 5,769,795.
The devices shown in the above referenced patents are intended to enhance ultrasonic visibility. Some of these devices are complex and expensive to manufacture. Some of these devices are difficult to manipulate within the patient such as the square rectangular shaped needle suggested in U.S. Pat. No. 5,611,345. Furthermore, many of the devices only marginally enhance ultrasonic visibility.
Accordingly, it is an object of this invention to provide a design for a medical instrument and in particular a needle which will provide enhanced imaging in a wide range of orientations between the axis of the needle and the ultrasonic echo sensor.
It is a further and related object of this invention to provide this enhanced imaging in a design that is simple and inexpensive to manufacture and relatively simple to operate.
These two objects are important in order to assure maximum usage of the invention in a large number and a wide variety of applications where an ultrasonically identified needle is important.
Furthermore, it is another related purpose of this invention to provide the above objectives in a design which provides no additional risk of trauma to tissue.
There are inevitable trade-offs to the design considerations to achieve the above interrelated objectives. Addressing all of these considerations calls for some tradeoff between the objectives.
Accordingly, it is a major object of this invention to provide an enhanced ultrasonically visible needle which achieves the objectives of low cost, simple structure, high visibility, high degree of safety and avoids complicated procedures or new techniques with which medical personnel are not familiar.
Most particularly, it is an object of this invention to achieve all of these objects with an enhanced trade-off value for the combined objectives.